Process for multi-layer coating

Abstract

A process for the production of a multi-layer coating, wherein a primer layer which is electrically conductive in the at least partially cured state is applied by electrodeposition from an electrodeposition coating agent (I) to an electrically conductive three-dimensional object, at least partially cured exclusively by the action of near infra-red radiation substantially only on the surfaces of the object exposed to the radiation, and an additional coating layer is applied by electrodeposition from an electrodeposition coating agent (II) which is different from electrodeposition coating agent (I), and then this additional coating layer as well as completely uncured or incompletely cured area parts of the primer layer produced from electrodeposition coating agent (I) are cured.

What is claimed is:  
     
       1. A process for the production of a multi-layer coating on the surfaces of an electrically conductive three dimensional object comprising the following steps: 
       (1) applying at least one primer layer to the surfaces of the object by electrodeposition from an electrodeposition coating agent (I);  
       (2) at least partially curing exclusively by the action of near infra-red radiation substantially only the primer layer on the surfaces of the object exposed to said radiation to form a primer layer that is electrically conductive in the at least partially cured state;  
       (3) applying an additional layer of coating by electrodeposition from an electrodeposition coating agent (II) which is different from electrodeposition coating agent (I) over the primer layer applied in step (1) that is at least partially cured; and  
       (4) curing both the primer layer and the additional layer on the object to form the multilayer coating on the object.  
     
     
       2. The process of  claim 1  wherein more than one primer layer is applied to the surfaces of the object by electrodeposition and each layer is at least partially cured exclusively with near infra-red radiation after application of the primer layer. 
     
     
       3. The process of  claim 1  wherein prior to curing the primer and the additional layer in step (4) at least one additional layer of coating is applied. 
     
     
       4. The process of  claim 1  wherein after curing the primer and the additional layer in step (4) at least one additional layer is applied. 
     
     
       5. The process of  claim 1  wherein curing of the primer and the additional layer in step (4) is accomplished by baking at an elevated temperature. 
     
     
       6. The process of  claim 1  wherein the electrodeposition coating agents (I) and (II) are different from one another and are individually selected from the group consisting of anodically electrodepositable coating agents and cathodically electrodepositable coating agents. 
     
     
       7. The process of  claim 1  wherein the primer layer from electrodeposition coating agent (I) in the at least partially cured state has a volume resistivity from 10 3  to 10 8  Ohm·cm. 
     
     
       8. The process of  claim 1  where the three dimensional objects have visible and non visible surface regions and are selected from the group consisting of automotive bodies, automotive body parts, truck chassis, agricultural machines, household appliance housings and small bulk goods. 
     
     
       9. The process of  claim 1  wherein the near infra-red radiation is infra-red radiation in the wave length range from 750 nm to 1500 nm. 
     
     
       10. The process of  claim 1  wherein the near infra-red radiation is provided by near infra-red radiation emitters with an intensity of more than 10 kW/m 2  to 10 MW/m 2 . 
     
     
       11. A process for the production of a multi-layer coating on the surfaces of an electrically conductive three dimensional object comprising the following steps: 
       (1) applying a primer layer to the entire surface of the object by a single electrodeposition from an electrodeposition coating agent (I);  
       (2) at least partially curing exclusively by the action of near infra-red radiation substantially only the primer layer on the surfaces of the object exposed to said radiation to form a primer layer that is electrically conductive in the at least partially cured state;  
       (3) applying a second layer of coating by electrodeposition from an electrodeposition coating agent (II) which is different from electrodeposition coating agent (I) over the primer layer applied in step (1) that is at least partially cured; and  
       (4) curing both the primer layer and second layer on the object to form the multilayer coating on the object.  
     
     
       12. The process of  claim 11  wherein prior to curing the primer and second layer in step (4) at least one additional layer of coating is applied. 
     
     
       13. The process of  claim 11  wherein after curing the primer and second layer in step (4) at least one additional layer is applied. 
     
     
       14. The process of  claim 11  wherein curing of the primer and second layer in step (4) is accomplished by baking at an elevated temperature. 
     
     
       15. The process of  claim 11  wherein the electrodeposition coating agents (I) and (II) are different from one another and are individually selected from the group consisting of anodically electrodepositable coating agents and cathodically electrodepositable coating agents. 
     
     
       16. The process of  claim 11  wherein the primer layer from electrodeposition coating agent (I) in the at least partially cured state has a volume resistivity from 10 3  to 10 8  Ohm·cm. 
     
     
       17. The process of  claim 11  where the three dimensional objects have visible and non visible surface regions and are selected from the group consisting of automotive bodies, automotive body parts, truck chassis, agricultural machines, household appliance housings and small bulk goods. 
     
     
       18. The process of  claim 11  wherein the near infra-red radiation is infra-red radiation in the wave length range from 750 nm to 1500 nm. 
     
     
       19. The process of  claim 11  wherein the near infra-red radiation is provided by near infra-red radiation emitters with an intensity of more than 10 kW/m 2  to 10 MW/m 2 .